Femtosecond ultrafast dynamics study on the photoemission performance of reflection-mode GaAlAs photocathode

The photoemission characteristic of reflection-mode GaAlAs photocathode has been investigated, while a convenient and nondestructive method for evaluating the photocathode performances will be introduced. In this paper, two same reflection-mode photocathode structures with different research methods are adopted. One way is using multi-information measurement system to measure the photoemission characteristic curve of GaAlAs photocathode. Another method is the femtosecond transient reflection spectroscopy. The ultrafast dynamics property of the GaAlAs carrier is studied with the femtosecond transient reflectivity change, and the quantitative calculating is also shown. According to the results of two experimental methods, we analyze some photoemission performance parameters, such as carrier lifetime, diffusion length etc. The results show that the surface electron escape probability P and the drift length L-DE are different, while are the same of the back recombination velocity S-v by the two method. In a word, compared with multi-information measurement system, the femtosecond ultrafast dynamics method is more suitable to research on the photoemission characteristic of reflection-mode GaAlAs photocathode which is no damage and accurate.